1. Field of the Invention
The invention relates to a heat pipe, and a method of manufacturing heat pipe, and especially relates to a heat pipe with a sintered powder layer as capillary structure and a method of manufacturing the same.
2. Description of the Prior Art
Heat pipes improve heat transfer efficiency by use of a capillary structure and the phase change of working fluid therein. The heat dissipation efficiency is much better than that based on single-phase heat transfer. Recently, the heat pipe has been applied to heat-dissipating components of 3C productions widely. However, in practice, the heat pipe often needs to be deformed by bending and pressing flat to meet the design for thin heat-dissipating module. According to experiment results, the heat dissipation efficiency of the heat pipe after greatly pressed flat or bent tends downwards. The reason therefor is that because the capillary structure sustains compressive stress and tensile stress during the bending and pressing process, peelings or cracks occur in the capillary structure inside the heat pipe. The capillarity force for the working fluid is therefore reduced even to failed to push the working fluid, which influences the performance of heat transfer of the heat pipe seriously. Furthermore, the tube wall at the inner side is under compressive stress to induce buckling thereon during the bending on the heat pipe. Especially for a thinner tube wall, the buckling occurs more probably. A slight buckling on the tube wall will change the flow path of the working fluid; a serious buckling on the tube wall will damage the capillary structure, even to make the capillary structure peel off from the tube wall, leading to a breach, stagnation and so on in the flow path of the working fluid. Hence, in the industry, the heat pipes are usually bent under the conditions of the bending angle less than 90 degrees and the value of the bending radius larger than three times the value of the diameter of the heat pipe. However, for the current tendency of miniaturization on electronic devices, it has been unavoidable to bend the heat pipes by large angle and small radius. Therefore, how to maintain a good heat transfer efficiency of the heat pipe after bent by large angle and small radius has been a challenge for the industry for a long time.